KAISERSLAUTERN, Germany – Police in the German state of Rhineland-Pfalz are warning residents to be on the lookout for small plastic strips placed on doors, a possible indication that one’s home may be targeted by thieves.

The clear strip is usually stuck between a door and its frame, an attempt to determine whether residents are away, especially now during the summer holiday season, the Rhineland-Pfalz said in a statement.

Residents are asked to call their nearest police station if they find one of these strips on their doors.